This invention relates to a low profile filter for use in ostomy and related appliances such as ostomy and ileostomy pouches.
Ileostomy and ostomy pouches or appliances have long been fitted with adsorbent filters designed to filter malodorous gases discharged into the pouch or formed in the pouch. These filters are generally based on use of adsorbent particles such as activated carbon incorporated into a matrix such as polyurethane foam or a fibrous web. Liquid by-pass through the filter or around the filter or gas by-pass around the filter device have been the areas of major concern. In order to prevent these events from occurring, the adsorbent filter is frequently protected by a liquid impermeable and gas permeable barrier layer or film with the barrier film heat-sealed along a peripheral edge to the ileostomy or ostomy pouch or like device to prevent liquid bypass. A specific design addressing the problem of liquid and gas by-pass is described in U.S. Pat. No. 4,274,848, which proposes the use of a porous filter pad protected on at least one face by a heat-sealable protective layer which is porous and resists soiling and particle contamination. In a preferred arrangement the heat sealable layer would be formed of a cellulosic material treated to be heat-sealable (KAYCEL) optionally with an additional porous thermoplastic film layer such as DELNET or GORTEX. When the porous filter pad is exposed to a liquid environment it is preferred that the outermost film of the protective layer facing the liquid be a thermoplastic film such as GORTEX. Liquid bypass is prevented by providing a flexible liquid barrier film (23) which is separately and continuously heat-sealed to the two protective layers covering both faces of the porous filter pad, which isolates the filter from the liquid. This barrier film is then further heat-sealed to the plastic film forming the ileostomy or ostomy pouch, preventing liquid by-pass around the filter. The filter itself is located on the inside face of the ostomy pouch. The porous filter pads are described as preferably a fibrous web of thermoplastic fibers mixed with carbon in a 50/50 blend. This appliance is extremely complicated to manufacture requiring numerous assembly steps and heat-sealing operations, additionally the filter itself is quite bulky and even placed on the inside face of the appliance can create an unsightly bulge on the wearer.
Other internally placed filters in ostomy appliances are described in U.S. Pat. No. 4,203,445, U.S. Pat. No. 5,250,042, and European Patent No. 358 316 B1. In U.S. Pat. No. 4,203,445 a filter is described which is similar to that described in U.S. Pat. No. 4,274,848, however, without the flexible liquid barrier layer(the two protective layers extend beyond the filter and tho two layers are heat sealed to the pouch wall) and the outward facing filter protective layer is provided with a series of holes to increase gas flow. Gas by-pass of this filter is possible. U.S. Pat. No. 5,250,042 protects its filter with a multi-layer film barrier which is heat-sealed to the ostomy pouch around the filter. Suitable barriers described are laminates of a thermoplastic film and a porous polytetrafluoroethylene film, both of which are described as gas permeable. The actual filter is not protected and comprises carbon impregnated polyurethane foam with two nonwoven cover layers adhered on both sides. This again, is a rather high profile filter and it requires complicated assembly and manufacturing steps in order to produce the finished appliance. European Patent No. 358 316 B1 describes a polyurethane foam impregnated with carbon which is housed in a rigid thermoplastic filter case. The filter case is in turn heat-sealed to the inside wall of the ostomy appliance. This is an extremely high profile heavy filter and would be somewhat costly and uncomfortable for the wearer.
U.S. Pat. No. 4,957,522 describes a conventional filter surrounded by a liquid impermeable gas permeable film. The filter is described as usable in container vents such as for radioactive material or an ostomy appliance. Either the two outer faces or the outer faces and the side portions of the filter are covered with the microporous or porous film. No specific filter or microporous film is specified.